1. Field of the Invention
The present invention relates to a non-contact transformer in which electrical current is transmitted between non-contacting first and second transformer components located in mutual opposition to each other.
2. Description of Background Information
Conventional transformer T, as shown in FIG. 6, includes a primary transformer component 3 installed within primary housing 2, and secondary transformer component 5 installed within secondary housing 4, the housing being oriented in mutual opposition to each other. Electromagnetic inductance, which occurs between primary coil 8 of primary transformer component 3 and secondary coil 9 of secondary transformer component 5, induces non-contact electrical current transmission between primary transformer component 3 and secondary transformer component 5. Due to its ability to provide non-contact electrical current transmission, non-contact transformer T can be provided for example, in an electrical appliance that is exposed to water such as an electric toothbrush or electric shaver shown as appliance X in FIG. 6, and into charging device Y which is used to electrically charge appliance X. The non-contact transformer allows charging device Y to safely supply electricity to the terminals on appliance X, even when appliance X is wet, without a physical connection being established between appliance X and charging device Y. With primary transformer component 3 installed within primary housing 2 to form charging unity Y, core space 1 is provided in secondary transformer component 5, instead of a solid ferrous core, in order to lower manufacturing costs, and the internal space of primary housing 2 is completely filled with resin 6 (FIG. 7) in order to improve heat dissipation and to waterproof the transformer. When resin 6 is poured into the internal space of primary housing 2, bottom plate 2a of primary housing 2 acts as the floor of the housing which is filled with resin 6. Because primary transformer component 3 is completely immersed within resin 6, core space 1 of primary transformer component 3 also becomes filled with resin 6.
It is desirable to bring primary transformer component 3 and secondary transformer component 5 into the closest mutual proximity to each other in order to obtain maximum electromagnetic inductance efficiency. To this end, the cylindrical end faces of primary housing 2 and secondary housing 4 (bottom plate 2a and 4a in this example) are brought into mutual contact. Terminals 12 are provided at the cylindrical end face of primary transformer component 3 opposite to bottom plate 2a of primary housing 2, and printed circuit board 7. As core space 1 is to be filled with resin 6, small gaps are provided between the respective cylindrical end faces of primary transformer component 3 where they meet bottom plate 2a of primary housing 2 and printed circuit board 7 in order to allow resin 6 to flow into core space 1. There is an inherent shortcoming, however, in that air core space 1 is a difficult space to fill with resin 6 because air present in core space 1 can become entrapped within resin 6 (residual air 15) with the inflow resin 6. The entrapment of residual air 15 within resin 6 can result in the distortion or breakage of primary housing 2 due to residual air 15 expanding from heat generated by the operation of primary transformer component 3.